In recent years, as display means for mobile display apparatuses and the like, reflection type liquid crystal display apparatuses (hereinafter referred to as “reflection type LCDs”) that use reflected natural light or room light (hereinafter referred to collectively as “external light”) and joint reflection/transmission type LCDs (hereinafter referred to as “semi-transmission type LCDs”) that use reflected external light when the amount of external light is high and light from a backlight when the amount of external light is low have come to be used from the viewpoint of reducing the electrical power consumption of the display means and thus making the battery smaller in size.
Out of mobile display apparatuses, display is required to be at high resolution and in full color for mobile telephones and portable computers in particular. For example, reflection type LCDs used in such mobile display apparatuses are required to have a high opening ratio to increase brightness and to display images with no parallax. The internal scattering/reflecting plate form reflection type LCD described in “FPD Intelligence, February 2000 edition (pages 66 to 69)”, for example, is known as a reflection type LCD that satisfies these requirements.
FIG. 16 is a schematic sectional view showing the constitution of this conventional internal scattering/reflecting plate form reflection type LCD.
In FIG. 16, the internal scattering/reflecting plate form reflection type LCD 10 is comprised of a pair of glass substrates 11 and 12 that transmit light, a reflecting film 15, described below, that is formed on an inner surface of the glass substrate 12 and scatters incident light 13 and reflects this light as reflected light 14, color filters 16 that are formed on an inner surface of the glass substrate 11 and transmit light of only a certain wavelength (color), and a liquid crystal layer 17 that is packed between the reflecting film 15 and the color filters 16 and controls the transmission of light.
Of the component parts of the internal scattering/reflecting plate form reflection type LCD 10, the glass substrate 12 and the reflecting film 15 together constitute a light-scattering/reflecting substrate 18.
FIG. 17 is a schematic sectional view showing the constitution of the light-scattering/reflecting substrate 18 appearing in FIG. 16;
In FIG. 17, the light-scattering/reflecting substrate 18 is comprised of the glass substrate 12, an internal scattering layer 20 that is formed on top of the glass substrate 12 and has a projecting shape, and a reflecting film 21 that is formed on top of the internal scattering layer 20 and has a shape that follows the projecting shape of the internal scattering layer 20. The reflecting film 21 reflects incident light, scattering the light due to the projecting shape. The internal scattering layer 20 and the reflecting film 21 together constitute the reflecting film 15 described above.
Methods for manufacturing such a light-scattering/reflecting substrate are disclosed, for example, in Japanese Patent No. 2698218, Japanese Laid-open Patent Publication (Kokai) No. 11-326615, and Japanese Laid-open Patent Publication (Kokai) No. 2000-267086, as described below.
First, a light-scattering/reflecting substrate manufactured using the manufacturing method disclosed in Patent No. 2698218, hereinafter referred to as “the first prior art”, is comprised of a glass substrate 30, an internal scattering layer 31 that is dotted over the glass substrate 30, and a reflecting film 32 that is formed on top of the glass substrate 30 and the internal scattering layer 31, as shown in FIG. 18. In this first prior art, the manufacturing method comprises a step in which a photosensitive resin, which is an organic substance, is applied onto one surface of the glass substrate 30, a step in which a large number of minute projecting parts are formed by patterning the applied photosensitive resin in a predetermined shape, masking, exposing to light and developing, a step in which the glass substrate 30 on which the projecting parts have been formed is subjected to heat treatment to round off angular portions of the projecting parts and thus form the internal scattering layer 31, and a step in which the reflecting film 32 made of an inorganic material such as a metallic material or a dielectric substance is formed on top of the glass substrate 30 and the internal scattering layer 31 by vapor deposition or sputtering.
Moreover, a light-scattering/reflecting substrate manufactured using the manufacturing method disclosed in Japanese Laid-open Patent Publication (Kokai) No. 11-326615, hereinafter referred to as “the second prior art”, comprises a glass substrate 700, a first internal scattering layer 701 that is dotted over the glass substrate 700, a second internal scattering layer 702 that is formed on top of the glass substrate 700 and the first internal scattering layer 701, and a reflecting film 703 that is formed on top of the second internal scattering layer 702, as shown in FIG. 19. In this second prior art, in addition to manufacturing steps equivalent to those of the first prior art, also carried out are a step in which the second internal scattering layer 702 is formed by applying the same kind of photosensitive resin as that used in the first internal scattering layer 701 on top of the first internal scattering layer 701, which has been formed by rounding angular portions of projecting parts formed on the glass substrate 700, and a step in which the second internal scattering layer 702 is subjected to heat treatment.
On the other hand, a light-scattering/reflecting substrate manufactured using the manufacturing method disclosed in Japanese Laid-open Patent Publication (Kokai) No. 2000-267086, hereinafter referred to as “the third prior art”, comprises a glass substrate 40, an internal scattering layer 41 formed on top of the glass substrate 40, and a reflecting film 42 formed on top of the internal scattering layer 41, as shown in FIG. 20. The internal scattering layer 41 comprises a layer 43 of a first resin, and a plurality of spherical parts 44 that are made of a second resin and are distributed through the upper part of the first resin layer 43. Because the spherical parts 44 are distributed through the upper part of the first resin layer 43, a large number of minute projecting parts are formed on the surface of the internal scattering layer 41. In this third prior art, the manufacturing method comprises a step in which a mixed resin liquid, in which are mixed the first resin and the second resin, which are organic substances that tend to separate out into separate phases to one another, is applied onto the glass substrate 40, a step in which the resulting mixed resin layer is made to undergo phase separation so that the internal scattering layer 41 having the large number of minute projecting parts formed on the surface thereof is formed, and a step in which the reflecting film 42 made of a metallic material is formed on top of the internal scattering layer 41 by vapor deposition or sputtering.
However, the light-scattering/reflecting substrate manufacturing methods of the first and second prior art described above are both based on a photolithography technique using a photosensitive resin. These manufacturing methods thus include steps of applying the photosensitive resin, masking, exposing to light, developing, carrying out heat treatment and so on, and hence there is a problem that the manufacturing process is complicated and thus the manufacturing cost is high.
The third prior art, on the other hand, is based on a resin phase separation technique, not on a photolithography technique, and hence the problem described above does not occur. Nevertheless, in the first to third prior art described above, the internal scattering layer has an organic material as a principal skeleton thereof, and hence there is a problem that adhesion to the reflecting film, which is made of an inorganic material such as a metallic material or a dielectric substance, is poor, and thus the reflecting film easily peels off. Moreover, when the reflecting film is formed by a vacuum film formation method such as vapor deposition or sputtering, there is a problem that components adsorbed on the surface of the internal scattering layer and unreacted components inside the internal scattering layer are discharged from the internal scattering layer as a gas, thus altering the optical properties (reflectance, refractive index, transmitted color tone etc.) of the reflecting film.
A method for manufacturing a thin film having as a principal skeleton thereof an inorganic material such as a metallic material or a dielectric substance that has good adhesion to such a reflecting film made of an inorganic material is disclosed, for example, in Japanese Patent No. 2901833.
The thin film manufactured by this manufacturing method is made from first and second sol solutions comprised of metal alkoxide compounds (or metal acetylacetonate compounds); a solution in which are mixed the first and second sol solutions is applied onto a glass substrate, thus forming a micropitted surface layer.
However, the projecting shape of the thin film formed through this method is controlled by the functional groups and molecular weights of the compounds in the two selected sol solutions. As a result, projecting parts having a diameter greater than about 200 nm cannot be formed, and hence it is not possible to use the thin film as an internal scattering layer that scatters visible light (wavelength 400 to 800 nm).
It is thus an object of the present invention to provide a projecting film and a manufacturing method thereof, which enable adhesion to a reflecting film made of an inorganic material to be improved, and alteration of the optical properties of the reflecting film to be prevented, and also enable the diameter of projecting parts to be controlled freely through few manufacturing steps.